Pennaceous wing feathers are known only in aviremigian maniraptors (oviraptorosaurs, deinonychosaurs, and avialians); even therizinosaurs appear to have only had long protofeathers (or plumaceous feathers) on the arms. As ornithomimosaurs weren't maniraptors proper, it looks as though they didn't have pennaceous feathers either, but protofeathers on the arms are deep within the realm of possibility (even probability).
Very nice image regardless; has to be one of my favorite Gallimimus depictions now.
Based on this, here is Paul's revised Gallimimus.
This was a little thing, but the kind of little thing that makes me happy. An example of constructive criticism and responsive artistry, an ideal to aim for as science and art proceed into a future made uncertain by the revolution in communication we're living through.